CS2000-OTP

DS758F1

17

5.4.6

Ratio Configuration Summary

time programmable memory. The M[1:0] pins or LockClk[1:0] modal parameter then select the user de-

fined ratio to be used (depending on if static or dynamic ratio mode is to be used). The resolution for the

mine the output to input clock ratio. The effective ratio is then corrected for the internal dividers. The fre-

quency synthesizer’s fractional-N source selection is made between the static ratio (in frequency

synthesizer mode) or the dynamic ratio generated from the digital PLL (in Hybrid PLL mode) by either the

FracNSrc modal parameter for manual mode or the presence of CLK_IN in automatic mode. The concep-

tual diagram in Figure 13 summarizes the features involved in the calculation of the ratio values used to

generate the fractional-N value which controls the Frequency Synthesizer. The subscript ‘4’ indicates the

modal parameters.

Figure 13. Ratio Feature Summary

Referenced Control

Parameter Definition

Ratio 0-3................................“Ratio 0 - 3” on page 23

M[1:0] pins............................. “M1 and M0 Mode Pin Functionality” on page 19

LockClk[1:0] .......................... “Lock Clock Ratio (LockClk[1:0])” section on page 23

LFRatioCfg ............................ “Low-Frequency Ratio Configuration (LFRatioCfg)” on page 24

RModSel[1:0] ........................ “R-Mod Selection (RModSel[1:0])” section on page 22

RefClkDiv[1:0] ....................... “Reference Clock Input Divider (RefClkDiv[1:0])” on page 24

FracNSrc ............................... “Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 23

Ratio Format

Frequency Reference Clock

(CLK_IN)

SysClk

PLL Output

Frequency

Synthesizer

Digital PLL &

Fractional N Logic

R Correction

N

Ratio 0

Ratio 1

Ratio 2

Ratio 3

12.20

20.12

12.20

only

M[1:0] pins

LFRatioCfg

Ratio

Modifier

Ratio

Modifier

Auto Selection

(CLK_IN sense)

Manual Selection

R Correction

RefClkDiv[1:0]

Timing Reference Clock

(XTI/REF_CLK)

Divide

RefClkDiv[1:0]

Static Ratio

Dynamic Ratio

M2 pin force Manual

or

M[1:0] pins =? LockClk[1:0]

≠

=

M2 pin